The invention pertains to a method and apparatus for the production of metal-free areas during the deposition of metal from the vapor phase onto a strip of insulating material intended for use in electrical capacitors. The area of the insulating strip which is to remain free of metal is covered by an endless cover strip, which rests on the insulating strip and is conducted along with it at the same speed. The cover strip is coated with oil on the side facing the metal evaporator before it enters the vapor deposition zone.
Apparatus of the type in question is known, in which a cover strip of paper or metal is conducted synchronously and in contact with the insulating strip so that metal-free areas can be produced on the strip of insulating material to be coated (U.S. Pat. No. 2,898,241).
A process for the production of metal-free areas on a strip of insulating material during the process of metal vapor deposition by means of which gradual transitions between the metal coatings and the metal-free areas are produced is also known (U.S. Pat. No. 4,478,878).